Diagnostic challenge of intrathoracic tissue misplacements: a thymic choristoma in a fetal lung

Choristomas (Gr. chōristos, ‘separated’) are well-delimited formations consisting of histologically normal tissue located in an abnormal anatomical site.1 Their aetiology is related to failures in the normal course of embryonic development of the neural tube. While choristomas are frequently encountered in some parts of the body (eg, thyroid gland, pelvis), an intrapulmonary localisation is rarer. In particular, the presence of thymic tissue in the lung has never been documented in the English literature. Here, we illustrate a choristoma composed of mature thymic tissue in the lung of a fetus who died after 16 weeks of gestation. A 21-year-old, gravida 1, para 0 woman experienced a spontaneous abortion at 16 weeks of gestation. Autoptic examination of …